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Version: 3.0

JSDOM crawler

This example demonstrates how to use JSDOMCrawler to crawl a list of URLs from an external file, load each URL using a plain HTTP request, parse the HTML using the jsdom DOM implementation and extract some data from it: the page title and all h1 tags.

import { Dataset, JSDOMCrawler, log, LogLevel } from 'crawlee';

// Crawlers come with various utilities, e.g. for logging.
// Here we use debug level of logging to improve the debugging experience.
// This functionality is optional!
log.setLevel(LogLevel.DEBUG);

// Create an instance of the CheerioCrawler class - a crawler
// that automatically loads the URLs and parses their HTML using the cheerio library.
const crawler = new JSDOMCrawler({
// The crawler downloads and processes the web pages in parallel, with a concurrency
// automatically managed based on the available system memory and CPU (see AutoscaledPool class).
// Here we define some hard limits for the concurrency.
minConcurrency: 10,
maxConcurrency: 50,

// On error, retry each page at most once.
maxRequestRetries: 1,

// Increase the timeout for processing of each page.
requestHandlerTimeoutSecs: 30,

// Limit to 10 requests per one crawl
maxRequestsPerCrawl: 10,

// This function will be called for each URL to crawl.
// It accepts a single parameter, which is an object with options as:
// https://crawlee.dev/api/cheerio-crawler/interface/CheerioCrawlerOptions#requestHandler
// We use for demonstration only 2 of them:
// - request: an instance of the Request class with information such as the URL that is being crawled and HTTP method
// - $: the cheerio object containing parsed HTML
async requestHandler({ request, window }) {
log.debug(`Processing ${request.url}...`);

// Extract data from the page
const title = window.document.title;
const h1texts: { text: string }[] = [];
document.querySelectorAll('h1').forEach((element) => {
h1texts.push({
text: element.textContent!,
});
});

// Store the results to the dataset. In local configuration,
// the data will be stored as JSON files in ./storage/datasets/default
await Dataset.pushData({
url: request.url,
title,
h1texts,
});
},

// This function is called if the page processing failed more than maxRequestRetries + 1 times.
failedRequestHandler({ request }) {
log.debug(`Request ${request.url} failed twice.`);
},
});

// Run the crawler and wait for it to finish.
await crawler.run([
'https://crawlee.dev',
]);

log.debug('Crawler finished.');